Conventionally, a surface protective layer and an interlayer insulating film for a semiconductor device use a polyimide resin having excellent heat resistance, electrical characteristics, mechanical characteristics, and the like. The polyimide resin has recently been used as a photosensitive polyimide precursor composition. The photosensitive polyimide precursor composition is easily coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and heat-imidized, and thereby, forms a surface protective layer, an interlayer insulating film, and the like.
Accordingly, the photosensitive polyimide precursor composition may remarkably shorten a processing time compared with a conventional non-photosensitive polyimide precursor composition.
The photosensitive polyimide precursor composition can be applied as a positive type in which an exposed part is developed and dissolved and a negative type in which the exposed part is cured and maintained. The positive type photosensitive polyimide precursor composition is preferably used, since a non-toxic alkali aqueous solution is used as a development solution. The positive photosensitive polyimide precursor composition includes a polyimide precursor of polyamic acid, a photosensitive material of diazonaphto-quinone, and the like.
However, the positive photosensitive polyimide precursor composition has a problem of obtaining no desired pattern, because the carboxylic acid of the polyamic acid is too highly soluble in an alkali.
In order to solve this problem, a material including a polybenzoxazole precursor and a diazonaphtoquinone compound has drawn attention (Japanese Patent Laid-open Publication No. S63-96162). However, when actually used as the polybenzoxazole precursor composition, film loss of an unexposed part is remarkably increased, hardly obtaining a desirable pattern after the development.
In order to improve this problem, if the molecular weight of the polybenzoxazole precursor is increased, the film loss of the unexposed part is reduced, but a residue (a scum) is generated during the development, deteriorating a resolution and increasing a development time on the exposed part.
In order to solve the problem, addition of a certain phenol compound to a polybenzoxazole precursor composition has been reported to suppress the film loss in unexposed parts during development (Japanese Patent Laid-Open Publication No. H9-302221 and Japanese Patent Laid-Open Publication No. 2000-292913). However, the suppression of the film loss in unexposed parts is insufficient. Accordingly, research on increasing the suppression of the film loss as well as preventing generation of the development residue (scum) is required. In addition, research on a dissolution-inhibiting agent is required, since a phenol compound used to adjust solubility is decomposed at a high temperature during curing, causes a side reaction, or the like and resultantly, does large damage on mechanical properties of a cured film.
On the other hand, the positive photosensitive resin composition including a polybenzoxazole precursor may be applied to an organic insulating film or a barrier rib material in a display device field. Many attempts have been recently made to develop a display device having high contrast ratio and high luminance. One of the attempts is to form a black filter layer between color patterns but has a problem of hardly realizing a high aperture ratio and bringing about low heat resistance and insulating properties. Thereafter, another attempt of securing a high aperture ratio by making a non-light emitting region black and simultaneously, improving a contrast ratio and visibility but has a problem of deteriorating inherent properties of an insulation layer because a colorant is dissolved in a large amount.
Of a colorant, an inorganic pigment as carbon black and the like used for a black mill-base, in general has excellent light shielding properties but has a problem of deteriorating insulating resistance properties, which is not appropriately applied to an insulation layer for an organic light emitting diode. An organic pigment relatively consists of a pigment mixture realizing a black color and thus, has better insulating resistance properties than the inorganic pigment but needs to be more included than the inorganic pigment in a photosensitive resin composition to accomplish equivalent light shielding properties and more possibly, deteriorates pattern developability and produces a residue.